Method of preparing gamma-dialkyl butyronitriles



Patented Jan. 4, 1949 UNITED STATES PATENT OFFICE METHOD OF PREPARING GAMlVIA-DIALKYL BUTYRONITRILES No Drawing. ApplicationJanuary 28,1948, Serial No. 4,934

Claims.

The invention relates to a method for preparing gamma-dialkyl butyronitriles. It deals with a method whereby alpha-cyanoethyl-alpha,alpha-dialkyl acetaldehydes are converted to gamma-dialkyl butyronitriles.

According to this invention, alpha-cyanoethylalpha,alpha-dialkyl acetaldehydes of the formula wherein R and R are alkyl groups, are decomposed in the presence of an organic peroxide with elimination of carbon monoxide. When carbon monoxide splits out of the aldehydo group, there results compounds of the formula CHCH2CH1CN These are valuable intermediates for the preparation of branched-chained compounds. By

hydrolysis by known methods they yield branched carboxylic amides, acids, and esters. By reduction they yield branched chain amines.

Typical organic peroxides which are suitab for effecting the decarbonylation are, by way of \CHOHO RI used as starting materials may have two identical alkyl groups as R and R or two 'difierent alkyl groups. The alkyl groups may be straight or branched. Typical groups are methyl, ethyl, propyl, butyl, isobutyl, amyl, hexyl, octyl, dodecyl,

and the like. It is preferred that the two groups together do not contain more than sixteen carbon atoms. It is also preferred to deal with compounds in which one of the groups does not contain more than nine carbon atoms and in which one of the alkyl groups is joined to the alphacarbon atom of the aldehydic compound at a primary carbon atom of said alkyl group.

The newly discovered reaction of this invention is not confined to monocyano alkylated acetaldehyde. It is also obtained with some cyanoethylated aldehydes in which another kind of substituent occurs in the alpha-position, such as benzyl or hexahydrobenzyl. Similarly, in place of one of the alkyl groups, there may be a cyanoethyl group. For example, alpha,alpha-di(2- cyanoethyl) propionaldehyde, which is formed by addition of two moles of acrylonitrile to propionaldehyde, may be decarbonylated with a peroxide catalyst to yield gamma-methyl pimelonitrile. The alpha-alkyl-alpha,alpha-di(cyanoethyl) pimelonitriles, fromwhich there are obtainable branched-chain dibasic acid derivatives and amines.

Typical dialkyl acetaldehydes from which the alpha-cyanoethyl alpha,alpha dialkyl acetaldehydes are prepared are isobutyraldehyde, alphamethyl butyraldehyde, alpha-methyl hexaldehyde, alpha-methyl octaldehyde, alpha-methyl dodecanal, alpha-ethyl butyraldehyde, alphaethyl hexanal, alpha-ethyl octanal, alpha-butyl butyraldehyd-e, alpha-butyl hexanal, alpha-butyl octanal, alpha-butyl isononanal, alpha-hexyl isononanal, alpha-heptyl isononanal, alpha-isoheptyl isononanal, etc. In each case the resulting cyanoethylated product contains the 2-cyanoethyl group in the alpha-position in respect to the aldehydo group.

The decarbonylation reaction of the alpha-(2- cyanoethyl) -alpha,alpha dialkyl takes place uponaddition thereto of an organic peroxide,which functions as a catalyst forthis reaction. The decarbonylation reaction occurs slowly at about 30 C. and is accelerated by heating the mixture. It is satisfactorily rapid at C. to C.

The peroxide may be added in an amount less than molecularly equivalent. From 1% to 20% of peroxide on the weight of the cyanoethyl dialkyl acetaldehyde usually give good results. If desired, small amounts of peroxide may be repeatedly added to the cyanoethyl dialykl acetaldehydo or aldehydo nitrile during the course of the reaction. This starting material may be exacetaldehydes thus yield gamma-alkyl acetaldehydes tended with an inert organic solvent and decarbonylation eifected with refiux of this solvent.

The following examples present typical procedures for the preparation of alpha,alpha-dialkyl butyronitriles from cyanoethyl dialkyl acetaldehydes.

Example 1 Cyanoethyl isobutyraldehyde,

(CH3)2C-GHO H2CH2CN was mixed with ten per cent of its weight of di-tert.-buty1 peroxide. This mixture washeated at 130 C. in a flask equipped with a reflux condenser. In about five hours the evolution of carbon monoxide ceased. The resulting reaction mixture was distilled. The fraction obtained at 155-156 C. at 758 mm. corresponded incompo' sition to GH-C H:CH2CN I C 3 It has a refractive index, N of 1.4048 and a density, d4, of 0.8009; The yield as obtainedunder" the above conditions :was' 30% of theory; This can be increased by the addition of a small amount of peroxide followed by continued heating.""

g H Example? I A mixture was made-from" 195 grams of ethyl 2-ethylhexa1dehyde,

- -C Ho-CHO momoN and 17.5 grains of di-tertL-butyl peroxide. This} w, mixture was stirred and heated atl28-132 C. in

a .fiask equippedwith a reflux condenser. At the end of sixhours the reaction mixture was washed with water and subjeoted to distillation under reduced pressure. A fraction of 61 grams was obtained at 100-102, ,C./9 mm. .which {corresponded in composition with C-zHr om'omomcmoHomomoN The product has an index of refraction-N13 of-.

1.4336 and a density, 114 of 0.8300. About" 60 grams of unchanged aldehydo nitrile used as starting. material was recovered.

Ewample 3 The procedure of Example'awas followed, but cyanoethyl-2-ethyl butyraldehyde was used as the starting material and of itsweightof hydroxyclyclohexyl hydroperoxide was adde'dlco From the reaction mixturethere was separated by fractional distillation a liquid in a yield of 40% boiling at 7 46? C'./9 mm., having a refractive index, NDZO, of 1.4258 and a density, 14

cyano- 1 4 of 0.8419. Its analysis'identified it as the com pound. a

, CzHa Q H E F In the same way other alpha-cyanoethylealpha,

alpha-dialkyl acetaldehydes are decarbonylated v when heated in the presence of a small amount with an organicperoxide as a catalyst anddecarbonylating said aldehydo nitrile. w

2. .A method for preparing gamma-dialkyl butyronitriles of the formula CHCHzCHzCN wherein R and R are alkyl groups of not over nine carbon atoms each, thesum of the carbon atoms in R and B, being not over sixteen, which 351comprises, treatingbetween C. and 15090;

with an organic peroxide as catalyst an aldehydo,

nitrile of the formula g R Rf( 3-OHO I OH CHzCN whereby there are formed carbon monoxide and a gamma-'dialkyl butyro'nitrile.

. 3. A" method for preparing gamma diethyl -butyronitrile'which comprises treating between- 30 C. and C. with an organic peroxide as catalyst the compound alpha-cyanoethyl-alphaethyl butyraldehyde and decarbonylating said compound. 1

4. A'method of preparing gamma-ethyl+gam-' ma-butyl butyronitrile which comprises treating between 30 C. and 150"; C. with an organic peroxide as catalyst the compound alpha-cyano y ethyl-alpha-ethyl hexaldehyde and decarbony lating said compound.

A method of preparing gamma-diamethyl Y butyronitrile which comprises treating between 30 C. and 150 C. with an organic peroxide as catalyst the compound alpha-cyanoethyl isobutyraldehyde' and decarbonylating said compound.

" HERMAN A. BRUSON,

THOMAS w. RIENER.

' No references cited 

